1. Field of the Invention
The present invention relates to signal processing for an image pickup device provided at a distal end of an insertion portion of an endoscopic apparatus
2. Description of the Related Art
An endoscopic apparatus generally has a light source (a light guide or the like) and an objective lens both attached to a distal end of an insertion portion; the light source illuminates the interior of the body cavity and the objective lens is used to capture observation images. An observation image formed by the objective lens is photoelectrically converted into an image signal by a solid image pickup device (for example, a CCD image sensor or a CMOS image sensor). The image signal is then transmitted to a camera control unit (CCU) and then subjected to various types of image processing such as white balance adjustment. The signal is finally displayed on a display section.
An observer operates an operation portion to insert the distal end of the insertion portion while bending the distal end so that the distal end conforms to the shape of the interior of the body cavity. The observer observes motion pictures and operates a shutter switch provided on an operation portion to display still images of seemingly necessary observation points.
CMOS image sensors are generally characterized by allowing single-chip manufacturing costs to be reduced more easily than CCD image sensors but being likely to distort picked-up images owing to restarting of charging immediately after reading of charges.